What happens if a suit is "closed out" as far as controls?
Consider an example:
If Opener is able to cuebid 3C (two of the top three clubs) and Responder is then able to cuebid 4C (the missing club honor), or backwards (Responder cuebids 3C to show one and then Opener cuebids 4C to show the remaining two), then the suit is "closed out," meaning that this side suit is proven to be A-K-Q at the top,
A similar auction could occur after Golady:
Opener and/or Responder could "close out" the diamond suit.
If that occurs, then a 5-level call in a closed out suit cannot logically be Exclusion RKCB, as that makes no sense. Furthermore, it cannot be a "shifting" RKCB (show the king and queen of this suit as the secondary key cards) for the reason of redundancy -- the answer to this question is already known. (Same principle of why a call cannot be exclusion if partner has already denied a control in that suit anyway). 6KCB makes just as little sense.
This auction, therefore, involving a "close out," offers an opportunity for a surrogate asking bid at above game in that strain.
Suppose, further, that the close-out occurs below game sufficiently low to enable more than one cue between the close-out call and game. (A simple example is closing out clubs with a 4C call when spades is the agreed strain.) My position is that any cue after a side suit is closed out should be a straight control cue (honor or shortness allowed) if control is not yet established and even if the normal cue rules for that side suit would (a) allow a cue of a queen or (b) discourage or not allow a shortness control cue. This would further not require any "two honors" rule.
An example. One partner of mine likes a 3NT cue in the specific auction:
3S(two top spades)-P-3NT
...to be a responsive spade cue (I have the missing spade honor). Or, if you will, the "definition" of a "serious 3NT" in this specific auction is "I have the missing spade honor."
But, once a 3NT call is made, closing out spades, it seems that Opener should be able to cue clubs with the Ace or King, but not the Queen, and that a cue of 4C could also be the call with a stiff or void in clubs. It just shows a club control. Similarly, a 4D cue by Opener should deny a diamond control but simply show a diamond control (Ace, King, stiff, or void).
Thus, closing out a side suit should convert other calls to straight control if control in that suit has not yet been established.